The Wayback Machine is an online service that takes screenshots from sites, allowing them users her to see how was a site at different times (what changes have been made during the years of its existence).

Most sites make frequent changes. The Wayback Machine allows you to you see content that no longer exists on a site. Η service can also be used to troubleshoot.
However, some sites may not be displayed because they are protected by code access (or for some other reason).
Go to the official Internet Archive website and enter the URL of the site you want to see in the address bar of the Wayback Machine. After entering the URL, click on "Search History".
Then you will see a schedule with all the years, for which there is a screenshot of the site you are looking for.
Select the year you want to view.
A calendar of the selected year will be displayed. Some dates in this year have a specific Colour. What does this mean:
- No color: No screenshot for this date.
- Blue: There is a screenshot for this date.
- Green color: Redirect (3xx).
Also, some circles in the calendar are larger than others. This means that the site has a lot of screenshots for the specific date (this does not represent the number of times the site was updated).
Select the date / time you want by placing the mouse cursor on the date and select the screenshot from the pop up menu that appears.
You are now able to browse the archived version of the site.
However, there are other solutions available for browsing older versions sites, As the oldweb.today, but the Wayback Machine contains the largest file from all the digital libraries available at Internet.

This was the process of browsing older versions of a site, as we read in Howtogeek.